GAINESVILLE, Fla. -- Summer cold sufferers take heart: A new University of Florida study offers new evidence that zinc -- the latest rage in cold remedies -- may provide immediate protection against disease.
"We were startled that the response in people was so dramatic and so rapid," said Robert J. Cousins, the Boston Family professor of human nutrition with UF's Institute of Food and Agricultural Sciences. "It was amazing that the levels of the genetic material we were studying went up after only one day on zinc supplements.
"This result suggests that part of the body's protective system is very sensitive to zinc. Although more research is needed, our findings are a major step toward proving that zinc supplements can help fight infections and protect people against stress."
Cousins worked with former UF doctoral student Vicki Sullivan on the research, which was published in the Journal of Nutrition in April.
The study is the first to apply genetic fingerprinting methods like those used in criminal and paternity investigations to understanding how nutrients directly affect the inner workings of human immune cells, Cousins said.
In the study, 12 men took 50 milligram zinc tablets -- the typical strength available in supplements -- every day for 18 days, and another 12 took a placebo. The participants' blood was drawn daily and analyzed for its ribonucleic acid, or RNA, the genetic code that tells cells to produce specific proteins.
The researchers focused on RNA that signals the body to produce a protein called metallothionein. The RNA rose the first day after participants took zinc and remained at least three times higher than it was before the study began.
The RNA levels dropped off immediately after the participants stopped taking zinc. "The body metabolizes zinc very rapidly," Cousins said. "It doesn't hold much useful zinc in reserve."
Zinc turns on metallothionein's ability to provide protection against infections, toxic chemicals and other stressors, according to earlier tests Cousins and other researchers conducted on animals.
"Our laboratory is trying to develop a sound scientific basis for saying that zinc has health benefits," said Cousins, whose research is supported by the National Institutes of Health.
Showing that benefit has not been easy. In fact, studies of zinc's effects -- including two recent studies on children -- have produced mixed results, leading the Food and Drug Administration to investigate claims about the benefits of zinc tablets and cough drops.
While zinc's benefits are being studied, Cousins suggests that people receiving chemotherapy for cancer be cautious. "Zinc's boost to the body's defenses possibly could reduce the effectiveness of their treatment," he said. "I would advise chemotherapy patients to consult with their oncologists before taking zinc supplements."
Cousins' research could lead to better tests for zinc deficiency, which has been tied to decreased immunity in the United States and to widespread infections in developing countries.
The best source of zinc in the diet is meat, although the mineral also is present in grain, beans and vegetables. "You can get a good amount of zinc through a healthy diet, but zinc supplements are worth considering, especially for people who don't include meat in their diet," Cousins said.